1. Field of the Invention
This invention relates to well tools and more particularly to means for equalizing pressures across well tools such as downhole safety valves, regulators, plugging tools, and the like devices.
2. Description of the Prior Art
Many well tools, such as tubing downhole safety valves, plugging tools, flow regulators, or the like, are installed in flow conductors of wells such as oil and gas wells by well-known means such as wireline tools, or the like, to control the flow of fluids therethrough. When it is desired to remove such a well tool from a well, the well is closed in to stop flow therefrom and facilitate the safe removal operation. Such well tools will generally hold back well pressure beneath, and often a great differential pressure will develop thereacross and must be equalized prior to removal from the well lest when the well tool is unlocked for removal, this differential pressure violently force the well tool and the wireline tools upwardly in the flow conductor. When this occurs, the tools generally become entangled in the wire, causing a long and expensive fishing job and loss of production.
Most such well tools or flow control devices include a seat and cooperative valve closure member. The valve closure is usually actuated between open and closed positions by an operator tube which is relatively longitudinally movable within the valve housing or body. In many such valves, this relative longitudinal movement of the operator tube also operates an equalizing mechanism so that pressure may be equalized across the valve closure prior to opening the valve and releasing it for removal from the well. In some tools, the equalizing mechanism is provided in a separate sub usually included between the flow control device and the locking device from which it is suspended in the well.
The following prior art U.S. patents were found in a search.
U.S. Pat. Nos. 3,071,151, 3,703,193, 3,845,818, 3,078,923, 3,731,742, 3,860,066, 3,273,649, 3,799,204, 3,865,141, 3,583,442, 3,799,258, 4,140,153, 3,696,868, 3,826,462, and 4,149,698.
Of these prior art patents, U.S. Pat. Nos. 3,860,066; 3,583,442; 3,696,868; 3,731,742; 3,826,462; 4,140,153; and 4,149,698 disclose well tools having a common type of equalizing valve. U.S. Pat. No. 3,860,066 is typical of this group.
U.S. Pat. No. 3,860,066 issued to Joseph L. Pearce, et al. on Jan. 14, 1975 discloses a safety valve in which a main valve and operator tube are disposed in a housing. The main valve cooperates with a seat surface surrounding the lower end of the bore through the operator tube and is movable in response to longitudinal movement of the operator tube between open and closed positions to control flow therethrough. An enlargement having an annular upwardly facing seating surface thereon is formed on the operator tube and engages an annular downwardly facing seating surface in the housing when the operator tube is in its upper or valve closed position to prevent fluid pressure bypassing the valve. These seat surfaces are hard and are subject to leaking.
A lateral equalizing aperture above the enlargement allows fluid pressure from below the valve to bypass it and enter the operator tube when the operator tube is depressed a little and the annular seats are disengaged.
This U.S. Pat. No. 3,860,066 also shows, in FIGS. 2, 3, and 4, that an operator tube which is longitudinally movable in a housing can be utilized to operate at least three types of main valves, namely, ball type, poppet type, and flapper type.
U.S. Pat. No. 3,703,193 which issued to George M. Raulins on Nov. 21, 1972 discloses a safety valve much like that just discussed but including a lost-motion connection incorporated in the operator tube between the main seat surface and the external equalizing seat surface. Thus, to open the valve, the operator tube is moved down a little to unseat the equalizing seating surfaces to permit equalizing of pressures. Afterwards, further downward movement of the operator tube is utilized to move the main valve to its open position. The seat surfaces in this valve also are hard and are subject to leaking.
U.S. Pat. No. 3,845,818 issued to Thomas M. Deaton on Nov. 5, 1974 and shows a safety valve having a housing, a flapper valve in the housing and an operator tube for moving the flapper valve to open position. The operator tube has an annular equalizing valve closure means on its exterior which engages an annular downwardly facing seat surface when the operator is in its upper position to prevent bypass of fluid pressure around the closed flapper valve. When the operator tube is depressed and the equalizing seating surfaces are disengaged, bypass fluid flow may occur through a lateral port in the housing, down through the equalizing valve mechanism, and through a lateral port in the operator tube, near its lower end. This is essentially an inversion of the equalizing means discussed above with respect to U.S. Pat. No. 3,860,066. The device of U.S. Pat. No. 3,845,818 has resilient seal rings which seal bubble tight, but the seal is broken before the equalizing valve is opened.
U.S. Pat. No. 3,799,204, issued Mar. 26, 1974 to Fred E. Watkins, and U.S. Pat. No. 3,799,258, issued also on Mar. 26, 1974 to Gilbert H. Tausch, disclose safety valves incorporating equalizing valves which operate much like that disclosed in U.S. Pat. No. 3,845,818, just discussed. The device disclosed in this patent has hard seats with a soft seal built into one of them. The seal is subject to being washed out of place as soon as the seal surfaces are disengaged.
U.S. Pat. No. 3,865,141, which issued to David E. Young on Feb. 11, 1975, discloses a safety valve having an equalizing valve in the operator tube. The operator tube has telescoping sections. When the operator tube is extended, the equalizing valve is closed. When it is telescoped or shortened, the seal is disengaged, and equalization of pressures can take place as a result of fluid flow therethrough.
U.S. Pat. No. 3,078,923 issued Feb. 26, 1963 to Gilbert H. Tausch and discloses a well safety valve having equalizing means which appears to be the showing most pertinent to the present invention. This patent shows a housing, a flapper valve in the housing, a lateral equalizing port above the flapper valve, and a spring-loaded equalizing valve closure in said port and having a portion thereof protruding into the bore of the housing. An operator tube is disposed for relative longitudinal movement in the housing. When the operator tube is in its upper position (see FIG. 3), its lower end clears both the flapper valve and the equalizing valves and allows them to be closed by their springs. To open the valve, the operator tube is depressed. It first engages and opens the equalizing valve and may apply an opening bias to the flapper valve. When equalization of pressures across the closed flapper has occurred, or nearly so, the operator tube will move further downwardly and will move the flapper valve to open position. The equalizing valve is opened before the flapper valve is opened and will remain open all the while that the flapper valve is open, allowing the well to be produced. The equalizing valve, being thus open during normal production, is vulnerable to being fouled with trash or detritis collecting therein. It is also subject to flow cutting and subsequent leaking when the flapper valve is closed and the safety valve is so desperately needed to hold against well pressure and perhaps prevent a disastrous blowout.
U.S. Pat. No. 3,071,151 which issued to Phillip S. Sizer on Jan. 1, 1963 shows an equalizing sub used in conjunction with a downhole safety valve. This equalizing sub has an equalizing valve built into a lateral aperture in the wall thereof and is structured almost identical to the equalizing valve built into the safety valve of U.S. Pat. No. 3,078,923, supra. The equalizing sub of U.S. Pat. No. 3,078,923 is shown on page 3908 of the Catalog of Oilfield Equipment and Services, 1962-63 Edition, where it is identified as the Type B or Type F Otis Equalizing Sub. The valves in these subs are actuated by a prong such as the Type "P" Prong illustrated on page 3938 of the same catalog. On page 3908 there is also illustrated the Type G Otis Equalizing Sub. While the Type B (or H) Otis Equalizing Sub has a poppet type valve with a metal-to-metal seal, the Type G Otis Equalizing Sub has a sleeve valve with resilient seals. The metal-to-metal seal is subject to leaking, and the resilient seals for the sliding sleeve valve are soon cut if the sleeve's port is moved past the seal while a pressure differential exists thereacross.
U.S. Pat. No. 3,273,649 which issued to Jack W. Tamplen on Sept. 20, 1966 discloses another type of equalizing sub. Tamplen's equalizing sub, also, has a sleeve valve actuable to open position by a prong, but when the prong is withdrawn from the device, it will return the sleeve valve to closed position and leave it there.
The present invention overcomes most of the problems associated with the equalizing mechanisms of the type found in the prior art discussed hereinabove by providing soft seals to form a bubble-tight bridge across the equalizing valve proper when the device is in closed position and then breaking this bridge just prior to opening the equalizing valve to permit flow therethrough.